Automotive and truck exhaust systems comprise a conduit for directing exhaust gas from the engine to a remote location. Such exhaust systems typically include a muffler, catalytic converter, resonator, or combination thereof for treating the exhaust gas before discharge to the atmosphere. Such exhaust systems must also be designed to fit around and otherwise be compatible with various drive trains, chassis sizes, body styles and the like. The exhaust gas conduit is therefore usually comprised of several exhaust tubes or pipes of various shapes and lengths which are connected together to form a path for the exhaust gas. The exhaust gas conduits in tractors and construction vehicles are typically shorter in length with the muffler often being secured directly to the exhaust manifold.
The most common way of joining pipes to construct an exhaust conduit is to utilize lap joints wherein tubes of a given end diameter are inserted into adjacent tubes of different end diameter, and then clamped in the region where the pipes overlap. Clamping means which encircle the outer tube are tightened down so as to clamp the outer tube onto the inner tube in the overlapping region of the tube ends. The ends of the outer tubes typically include a number of longitudinal slots spaced about its circumference in order to facilitate deformation and inward crimping onto the end of the inner tube telescoped therein by action of the clamp.
Such clamps, of course, must provide a substantially leakproof as well as mechanically secure joint. Any leakage of exhaust gas at the joints presents a safety hazard because of escaping noxious fumes, and a noise problem because of the pulsating nature of the flow through the conduit. Since a number of such joints occur in most exhaust systems, it is also desirable that such clamps be inexpensive and easy to install, and if possible also easy to disconnect and reinstall if and when it later becomes necessary to replace a portion of the associated exhaust conduit. Such clamps are therefore very important components in exhaust systems.
A variety of clamps have been developed heretofore for use with lap joints, particularly those in exhaust systems. The most common clamping means is the so-called guillotine or saddle type clamp. This clamp comprises a U-bolt having a radius of curvature substantially equal to the outside radius of the outer tube, and a saddle with a similar radius which slides onto the legs of the U-bolt. The saddle and U-bolt are forced towards each other by means of a pair of nuts threaded onto the ends of the U-bolt legs to squeeze the overlapping ends of the tubes therein. The nuts must be tightened evenly to avoid distorting the joint, and this requires additional time and attention during assembly. U.S. Pat. No. 2,719,345 is illustrative of the prior art in this regard. Since some type of slots in the outer tube are usually necessary to provide for deformability, it can sometimes be difficult to achieve uniformly good leakproof joints with such clamps. The slots can be eliminated with very heavy duty clamps which are capable of deforming a bead through the outer tube into the inner tube, such as that shown in U.S. Pat. No. 4,183,122; however, higher installation torques are required and permanent tube deformation leads to difficulties later on because the joint cannot be readily taken apart for service and maintenance, such as for replacing a muffler.
More recently, improved leakproof clamps have been developed which surround the lap joint and extend past and around the end of the outer tube onto the inner tube. U.S. Pat. Nos. 3,944,265 and Re. 30,042 disclose a clamp having a band of ductile metal which, when stressed beyond its elastic limit, conforms intimately with the tubes about their entire circumferences. This clamp, however, requires special materials or an additional gasket seal and tends to be more expensive, and is thus not completely satisfactory in all cases.
There is thus still a need for an improved clamp which provides better production and installation efficiencies and which facilitates construction of secure, substantially leakproof lap joints in exhaust systems.